Apparatus for deep-fat cooking

ABSTRACT

A new process and apparatus for the continuous deep-fat cooking of a food to produce a processed comestible wherein the food is passed through an elongated cooking zone. Hot cooking oil is introduced and withdrawn from the cooking zone at a plurality of points to produce hydraulic effects which insure proper contact of the food with the cooking oil.

United States Patent .1191

Wright et al.

[ APPARATUS FOR DEEP-FAT COOKING [75] Inventors: Edward S. Wright,Pittsburgh, Pa.;

John W. Angatadt, Williamsville; Gerard L. Garrow, Buffalo, both of N.Y.

[73] Assignee: Blew-Knox Company, Pittsburgh,

[22] Filed: Jan. 21, 1971 [21] Appl. No.: 108,303

52 US. Cl. ..99/403 [51] 161. c1. A473 37/12 [58] Field 61 Search99/403, 404, 405,

[56] References Cited UNITED STATES PATENTS 1451 Aug. 28, 1973 3,026,8853/1962 Eytinge 99/405 x 3,209,678 10/1965 Benson 61 al. 99/406 3,309,9813/1967 B61180]! 61 a]. 991407 x 3,641,924 2/1972 Sijbring 99/406 PrimaryExaminer-John Petrakes Assistant Examiner-Arthur 0. HendersonAttorney-Mam & Jangarathis [57] ABSTRACT 1,707,786 4/1929 Ehrhart 99/40612 Claims, 3 Drawing Fi um l6 7 T L I26 .96 H.9a /a 76 g 122B 7/ a 70so: :66 54 40 2a 32 2:0 5 x721: 91 lmu fll \2 5 78 W I \V g 1/4 PATENTEDAUG 28 M3 N 0000006 \ooocooo 000000 ououooo OOOO SHEET 1 0F 2 l g g g gINVENTORS Edward 8. Wright John W. Angsfodf BY Gerard L. Gorrow Thisinvention relates to a new apparatus for the cooking of foods, and moreparticularly to a new process and apparatus for the deep-fat cooking offoods to produce processed comestibles, such as potato chip and likeproducts.

BACKGROUND OF THE INVENTION Early processes for continuously deep fryingpotato slices and the like to produce potato chips utilized elongatedcooking troughs or kettles containing a cooking oil which was heated bythe direct contact of hot gases with the underside of the kettle bottom.Potato slices and other like materials to be processed were floatedalong the surface of the cooking oil and pushed throughout the length ofthe kettle by spaced-apart pusher assemblies.

More recent processes employed elongated troughs or kettles wherein thecooking oil was separately heated, either directly or indirectly e.g., aboiler or heat exchanger and passed to the cooking apparatus. A majorportion of the oil was introduced into the kettle at the slice-receivingend of the kettle, withdrawn from the other end, reheated andre-introduced into the kettle. With due consideration to heat transferrequirements, i.e., sensible heat required to raise the potato slice tocooking temperatures, latent heat required to vaporize the water contentof the slices, maximum temperature to which the cooking oil may beheated without excessive break down thereof to free fatty acids, etc.,in view of the cooking time required for an average size potato slice,it was necessary to provide mechanical restraining devices, such asrotating flow wheels, rakes or submerger belts, intermediate the ends ofthe kettle to provide the necessary residence time for dewatering thepotato slices (about 80 percent by weight of the slice) and for cookingthe potato slices. This resulted in an oil flow rate through the kettleof about to 6 times the rate of flow of the potato slices where aresidence time of from about 3 to 4 minutes is required to produce anacceptable product. Final cookingof the slice is generally thought to bethe reduction of the water content from about 10% to about 2% which isthe moisture content of an acceptable product.

In many of the prior art apparatus, the potato slice had a tendency toadhere to the surface of the kettle as well as to the mechanicalrestraining devices in the early stage of cooking when the potato sliceis in a pliable plastic state causing a dam effect thereby resulting inthe development of areas of high cooking'oil velocities in the clearancebetween the restraining mechanisms and the bottom and sides of thekettle. Some slices would surge through the areas of such high veloc-'ity and would not be retained in the kettle for a time sufficient to beproperly cooked. Such high velocities of cooking oils created by thedamming effect also had a tendency to develop eddies or whirlpools whichwould excessively restrain some of the slices being processed to theextent that the resulting chip was overcooked, and in some instancesburnt thereby requiring manual removal prior to packaging. Breakage ofan overcooked or burnt chip would result in fines in the cooking oil andfines in the cooking oil tend to break down the oil and form free fattyacids which are detricessitate high oil flow rates to provide for properheat levels for final cooking of the slice.

' SUMMARY OF THE INVENTION It is an object of the invention to provide anew apparatus for the deep-fat cooking of foods to produce processedcomestibles, such as potato chips and like products.

Another object of the invention is to provide a new apparatus for thedeep-fat cooking of foods which will reduce cooking times and form amore uniform product.

Still another object of the invention is to provide a new apparatus forthe deep-fat cooking of foods whereby improved thermal efficiencies areachieved.

A further object of the invention is to provide a new apparatus for thedeep-fat cooking of foods which will reduce cooking oil requirements perunit weight of product than heretofore achieved.

A still further object of the invention is to provide a new apparatusfor the deep-fat cooking of foods which will substantially reduce thequantity of fines produced.

These and other objects of the invention are achieved in an elongatedtrough or kettle wherein a major portion of the cooking oil isintroduced into the kettle at the food-receiving end over a large areain essentially countercurrent contact to the food slices beingintroduced into the kettle. The food slices initially fall towards thebottom of the kettle but are caused to move gently upward by thehydraulic force of the rising cooking oil which helps to separate thewet slices as the violent boiling action is initiated by the formationof water vapor. The slices pass into a second zone of the kettleincluding an agitating means and a means for introducing a secondportion of heated cooking oil from a plurality of points above thesurface of the cooking oil which effects another hydraulic force tocause the slices to tumble to insure that all surfaces are properlyexposed to the cooking oil. In this second zone, a portion of thecooking oil is withdrawn and passed to a subsequent zone. The slicesmove to a third zone wherein the final cooking thereof is effected atcontrolled cooking oil temperatures most effective for completion of thecooking process. In the third zone, the slicesare subjected to a furtherhydraulic effect by the introduction of cooking oils withdrawn from thesecond zone. By the continuous introduction into the kettle of cookingoils at controlled temperatures and flow rates in accordance with thepresent invention, the cooking time of the slice may be reduced by asmuch as 33 percent with an increase in capacity for a given kettle sizeby as much as 5% per square foot of surface areacompared with prior artprocesses. The concentra tion of slices in the cooling oil results inwhat may be called a slurry which is dense enough for essentially plugflow thereby producing a more uniform product.

mental to the flavor and shelf life of the product. Additionally, highheat levels required at the inlet end ne- Since the oil turnover rate,i.e., oil absorbed into the slices, is increased by the greaterproduction rate in a like size kettle which reduces the length of timeoil remains in the system, the tendency of the oil to break down andform free fatty acids is reduced which permits the preparation of aproduct having a longer shelf life. Additionally, the hydraulic effectsproduced in accordance with the invention achieve improved heat transferrelationships between the slices and cooking oils since temperaturegradients at any given crosssectional point in the kettle are minimizedas compared to prior art apparatus wherein temperature stratificationdue to the damming effect was commonplace. For ease of understanding,the invention will be described with reference to the treatment ofpotato slices to produce potato chips, it being understood that otherfoods suitable for deep-fat cooking may be also used. It will beappreciated from the following description of the invention that thetemperature of the hot oil at various points in the kettle may becontrolled to any necessary degree by the valving arrangement to permitmixing of oil streams at difierent temperature levels to achievetemperature levels proper for the treatment being effected, i.e.,initial evaporation ofa portion of the water content of the slice, andcooking. It is understood that not all of the water content iseliminated from the processed comestible.

BRIEF DESCRIPTION OF THE DRAWINGS Further objects and advantages of theinvention will become apparent upon consideration of the detaileddisclosure thereof, especially when taken with the accompanying drawingswherein like numerals designate like parts through:

FIG. 1 is a schematic side sectional view of the apparatus of theinvention and a schematic flow diagram of the process for the deep-fatcooking of foods;

FIG. 2 is a sectional top view of the apparatus partially schematictaken along the lines 22 of FIG. 1; and

FIG. 3 is an enlarged cross-sectional view of the receiving end of theapparatus taken along the lines 3-3 of FIG. 1.

Referring now to the drawing there is illustrated a cooking apparatus,generally indicated as 10, comprised of an elongated trough or kettle l2suitably sheathed with heat insulating material (not shown) having areceivine end and a delivery end, generally indicated as R and D,respectively. The surface level of the cooking oil and product beingprocessed in the kettle 12 is indicated as L. The top of the kettle 12is partially enclosed with a hook 14 having a vent 16. A deflector plate18 for condensate removal is suitably mounted (not shown) with the hood14 below the vent 16. Within the receiving end R of the kettle 12, thereis positioned an oil distribution means, generally indicated as 20,comprised of a plate 22 having a plurality of orifices and forming anoil distribution zone 23 with the bottom and side walls of the kettle12. The angle of the plate 22 may be varied by an adjusting means (notshown) depending on desired cooking conditions, as more fullyhereinafter discussed. Below the plate 22, the bottom of the kettle 12is provided with a oil inlet manifold 24 (See FIG. 3). Downstream of thedistribution plate 22, weirs 26 are provided extending crosswise to thelength of the kettle 12.

A chip agitator means, generally indicated as 28, is providedintermediate the ends R and D suitably mounted to a drive assembly (notshown) to effect a vertical reciprocating motion. The chip agitator iscomprised of plurality of horizontally extending bars 30 mounted to anupper support member 32 by a plurality of hangers 34. Below the uppersupport member 32 and above the surface of the cooking oil L, there isprovided an oil distribution means, generally indicated as 40, comprisedof an inlet manifold 42 extending across the kettle 12 with a pluralityof longitudinally extending conduits 44 having orifices therein (notshown) suitably mounted thereto. Below the oil distribution means 40,the bottom of the kettle is formed with a perforated plate 46 forming anoil collection zone 48 with a bottom plate 50, triangularly shaped sidewalls 52 and a front wall 54 (See FIG. 3). The front wall 54 is providedwith an outlet manifold 56.

Between the chip agitator means 28 and the delivery end D of the kettle12, there is provided a rake means, generally indicated as 60, of adesign known to those skilled in the art, such as that illustrated in U.S. Pat. No. 2,085,494 to Joseph D. Ferry, entitled Impeller Mechanismfor Cooking Apparatus. The rake means 60 is comprised of a plate 62having a plurality of orifices (not shown) formed therein and aplurality of downwardly extending fingers or prongs (not shown) affixedto the bottom. The plate 62 is mounted to a support assembly 64 bysupport bars 66 and is caused to move in an oval or elliptical path by adrive means (not shown) with movement being essentially clockwise to theaxis of the rake means 60 when viewing FIG. 1. Positioned above theperforated plate 62 there is provided a fluid distribution means,generally indicated as 68 comprised of a troughed plate 70 having aplurality of perforations, and a manifold 71 having conduits 72extending downwardly therefrom to a point above the troughed plate 70.Below the chip delivery end D and at the bottom of the kettle 12, thereis provided an outlet manifold 75.

Above the receiving end R of the kettle 12, a feed conveyor 76 ispositioned for introducing the slices into receiving end R. Positionedabove the conveyor 76 is a slice separator, generally indicated as 77comprised of a cylinder 81 having a plurality of flexible extensions orfingers 83. The slice separator is caused to rotate clockwise by a motormeans (not shown) at a rotational velocity greater than the linearvelocity of the belt of conveyor 76 to separate the slices to reduce thenumber of chips withdrawn from the kettle having soft centers. Thedelivery end D is provided with a discharge conveyor 78 having aplurality of outwardly extending fingers or prongs 79 which assist inremoving the chips from the kettle 12. The assemblies for forming potatoslices from whole potatoes (i.e., washer, peeler, slicer, etc.) and forpackaging the potato chips do not constitute a part of this inventionand are of the type presently known and used by those skilled in theart.

Referring now to FIG. 1 wherein there is illustrated a schematic flowdiagram of the invention, the'major components thereof include inaddition to the cooking apparatus 10, a heater 80, an oil storage tank82, a

strainer tank 84, and a liquid leveling device 86. The

heater 80 is in fluid communication by line and line 92 under thecontrol of valve 94 with inlet manifold 24, and by line 90 and line 96under the control of valve vwith the oil distribution means 40. Theoutlet manifold 56 of the kettle 12 is in fluid communication throughline 100 by pump 102 and line 104 with inlet manifold 71 by line 106under the control of valve 108. The outlet manifold 75 is in fluidcommunication by line 110 with strainer tank 84 wherein fines areremoved from the circulating oil. The strainer 84 is connected by line112 and pump 114 to heater 80 through line 116.

The liquid leveling device 86 is in fluid communication with kettle 12by line 118. The storage tank 82 provides a source of oil to levelingdevice 86 through line 1 18 by pump and acts as a surge tank for leveldevice 86 by line 122. Lines 104 and 110 are in fluid communicationtherebetween by line 124 under the control of valve 126 for adjustingheat requirements, as more fully hereinafter discussed.

In operation, hot cooking oil at a temperature of from about 335 to370F. is introduced into the kettle 12 through the manifold 24 into thezone beneath the plate 22 from heater 80 by lines 90 and 92. The heater84 is illustrated as being of the direct fired type; however, it isunderstood that a heat exchanger'may be employed wherein the cooking oilis heated by indirect contact with an intermediate heat transfer fluid.

Potato slices are passed to the kettle 12 by conveyor 76 from which theslices drop into the receiving end R of the kettle 12 and contactcountercurrently the hot cooking oil passing upwardly through theorifices of plate 22. As mentioned above, the angle of the plate 22 maybe varied dependent upon the material being treated, residence time,cooking temperatures, and the like. After the initial impact of theslices into the cooking oil, the slices are agitated by the upwardhydraulic effect of the cooking oil being introduced over a wide areawhich effect help to separate the wet potato slices as the violentboiling action caused by water vapor being released from the slices. Asis known to those skilled in the art, the greatest heat requirements areduring the initial contact of the potato slices with the cooking oilwhen 25 percent of the moisture of the potato slice is removed and iseasily achieved by the present invention. This initial treatment will behereinafter some time referred to as phase I cooking.

The potato slices will form a bed, generally of from 3 to 4 inches ormore which moves continuously towards the discharge end D of the kettle12. The slices and hot cooking oil pass over the weirs 26 which togetherwith the effect of the vertical reciprocating movement of the bars 30 ofthe agitator 28 further cause the slices to tumble to assure exposure ofall surfaces of the slices to the cooking oils. As the bed of slicesmoves into the intermediate portion of the kettle 12, the bed iscontacted with an additional quantity of cooking oil in the form of aplurality of streams thereof from the liquid distribution means 40. Thestreams of cooking oils provides another hydraulic effect to tumblefurther the slices to expose all surfaces of the slices to the cookingoil. As mentioned hereinabove, such hydraulic effects minimize adherenceof the slices to the surface of the kettle and to each other when theslices are in a pliable plastic state.

A portion of the cooking oil introduced into the ketstarting point(essentially a clockwise movement). During this essentially leftwardmovement, the fingers or prongs engage and move the slices, thusassisting the oil flow in traversing the slices through phase IIIcooking. Additional cooking oil in line 106 is supplied by manifold 71through conduits 72 onto the trough plate 70 from which the oil passesthrough the orifices onto the I rake plate 62 and thence to saidoil-slice bed through tle from the heater by line 90 is withdrawn fromkettle 12 through perforated plate 46 via outlet manifold 56 and ispassed through line 100 by pump 102 for subsequent use as more fullyhereinafter described. During passage of the bed of slices through theintermediate section of the kettle 12 further dewatering of the slice iseffected and such passage will hereinafter some time be refereed to as"phase ll cooking".

The bed of slices thereupon pass into the last section or zone of thekettle 12 wherein completion of the cooking of the slices is effected,hereinafter some time referred to as phase III cooking. The rotationalmovement of the rake means 60 is such to effect an essentiallyelliptical movement of the rake plate 62 whereby the fingers or prongsthereof dip into the bed of slices, move to the left (FIG. 1) and thenelevated from the surface of the material and returned to the theorifices therein. It will be noted that a portion or all of the cookingoil introduced onto the plate is the cooking oil removed from the kettle12 in line 100. The now-cooked slices or chips pass to the deliveryconveyor 76 whereat the prongs or fingers 79 affixed to the conveyorbelt of the'conveyor 78 assist in withdrawing the chips from the cookingoil. Cooking oil in discharge end D is withdrawn from manifold means andpassed by line 110 to strainer 84 wherein fines are removed. The cookingoil is withdrawn from strainer 84 in line 112 by pump 114 and is passedthrough line 116 to heater 80 wherein the cooking oil is raised to therequired temperature level for re-introduction into the kettle l2.'

The oil leveling device 86 is connected to a remote sensing device (notshown) which measures the level of cooking oil and slices in the kettle12. The leveling device 86 is in fluid communication with storage tank82 (continuously or discontinuously) by pump 120, Le, pump continuouslyrunning or activated in response to a signal from the remote sensingdevice. Should the remote sensing device be activated in response to alevel belowv thepreselected level L, cooking oil is introduced into thekettle 12 by line 118 from storage tank 82 under the control of theleveling device 86 until the preselected level L is reached, at whichpoint the fluid flow through the line 118 is discontinued.

It will be appreciated from the conduit and valving arrangement that thetemperature of the oil may be controlled to any necessary degree toprovide control of the oil temperature within the kettle 12 at the mosteffective temperature level for accomplishing the desired purpose in thevarious cooking phases. For instance, there are greater heatrequirements in phase 1 cooking wherein the temperature of the slices isfirst raised to 212F. at which point the water contained in the slicesbegins to vaporize and wherein vaporization of water in the slices iseffected to the extent that approximately 25 percent thereof is removed.A high temperature level of the cooking oil is desirable for phase IIcooking wherein the slices are further dewatered whereas lowertemperature levels of the cooking oil for phase III cooking is generallypreferred particularly from the standpoint of the color of the finalproduct. For instance, with potato slices having a high sugar content,it is desirable to have a low temperature level in phase III cooking toprevent overcooking (excessive carmelization of the sugar) whereby adark brown product results. Thus, the temperature level in phase IIIcooking is varied by proportioning the flow of cooking oil withdrawn inline between lines 106 and 124. For higer temperature levels, the ratiobetween the flow of cooking oil in line 108 to line 124 is increasedwhereas for lower temperature levels the ratio is decreased. lt isunderstood that all of the cooking oil withdrawn in line 100 from kettle12 may be passed to the phase Ill cooking stage.

The term countercurrent contact is used to described the relationshipbetween the direction of flow of the chips into the kettle 12 and thedirection of flow of cooking oil being introduced into the zone in whichchips and oil contact therebetween; i.e., greater than be merelyillustrative and the invention is not to be regarded as limited thereto.

EXAMPLE I Potato 'slices having a 20.0% solids content were introducedat a feed rate of 2540 pounds per hour into a kettle 29 feet long and 1foot wide. Cooking oil at a temperature of 358F. was introduced at therate of 177 GPM and 73 GPM into the kettle through lines 92 and 96,respectively. The desired residence time for the potato slices beingtreated was determined to be between 150 to 180 seconds. Cooking oil ata temperature of 326F. was withdrawn at the rate of 200 GPM and passedto manifold 71. Cooking oil at a temperature of 314F. was withdrawn atthe rate of 250 GPM from kettle 12 through outlet manifold 75. Thepotato chips withdrawn from the kettle 12 by the conveyor 78 hadexcellent color and taste.

It will be understood that the ability to alter the angle of the baffleplate 22 with the resultant alteration of the hydraulic effect of thecooking oil is one important factor in controlling the flow rate of thechips for proper residence time for cooking the slices which isdependent on various considerations including age of the potato afterharvest. The process and apparatus of this invention provides thecontrol of and assurance of proper temperature levels to suit therequirements of the local market under varying conditions of the potatoslices being treated. It will be appreciated that by reducing thevelocity of the cooking oil through the kettle essentially eliminatesthe whirlpools and eddy currents of the prior art apparatus and theirdeleterious effect.

Numerous modifications and variations of the invention are possiblewithin the above teachings and therefore the invention, within the scopeof the appended claims, may be practised other than as particularlydescribed.

We claim:

I. In an apparatus for treating a comestible with heated cooking oilincluding an elongated kettle having comestible feed means forintroducing said comestible into one end of said elongated kettle, theimprovement which comprises an oil distribution means in said one enddisposed beneath said comestible feed means for introducing said oil incountercurrent contact to said comestible over a wide area of said oildistribution means.

2. The apparatus as defined in claim 1 wherein said oil distributionmeans comprises a plate having a plurality of orifices therein andcontiguous with the bottom of said kettle, and wherein an oil inletzone.is

,formed by said plate and the bottom of said kettle.

3. The apparatus as defined in claim 1 wherein a weir means is disposedtransversely across the bottom of said kettle downstream and approximateto said oil distribution means.

4. The apparatus as defined in claim 3 wherein a second oil distributionmeans is provided intermediate the ends of said elongated kettle.

5. The apparatus as defined in claim 4 wherein said second oildistribution means is disposed above the surface level of the chip-oilslurry and includes a manifold having mounted thereto longitudinallyextending conduits including orifices therein.

6. The apparatus as defined in claim 12 wherein a third oil distributionmeans is provided in the end portion of said kettle opposite the endinto which said comestible is introduced.

7. The apparatus as defined in claim 6 wherein said third oildistribution means is disposed above the surface level of the chip-oilslurry and includes a plurality of longitudinally extending troughplates having orifices therein.

8. The apparatus as defined in claim 6 wherein an outlet manifold meansis provided in said kettle intermediate the ends of said kettle and isin fluid communication with said third oil distribution means.

9. The apparatus as defined in claim 8 wherein said outlet manifoldmeans is generally disposed beneath said second oil distribution meansand includes a perforated plate means.

10. The apparatus as defined in claim 8 wherein a second outlet manifoldmeans is provided in said kettle in the end thereof having said thirdoil distribution means and is in fluid communication with a heatingmeans for raising the temperature of said oil to that necessary to treatsaid comestible.

l l. The apparatus as defined in claim 10 wherein said heater means isin fluid communication with said first oil distribution means.

12. The apparatus as defined in claim 10 wherein said heater means is influid communication with said first and second distribution means.

1. In an apparatus for treating a comestible with heated cooking oilincluding an elongated kettle having comestible feed means forintroducing said comestible into one end of said elongated kettle, theimprovement which comprises an oil distribution means in said one enddisposed beneath said comestible feed means for introducing said oil incountercurrent contact to said comestible over a wide area of said oildistribution means.
 2. The apparatus as defined in claim 1 wherein saidoil distribution means comprises a plate having a plurality of orificestherein and contiguous with the bottom of said kettle, and wherein anoil inlet zone is formed by said plate and the bottom of said kettle. 3.The apparatus as defined in claim 1 wherein a weir means is disposedtransversely across the bottom of said kettle downstream and approximateto said oil distribution means.
 4. The apparatus as defined in claim 3wherein a second oil distribution means is provided intermediate theends of said elongated kettle.
 5. The apparatus as defined in claim 4wherein said second oil distribution means is disposed above the surfacelevel of the chip-oil slurry and includes a manifold having mountedthereto longitudinally extending conduits including orifices therein. 6.The apparatus as defined in claim 12 wherein a third oil distributionmeans is provided in the end portion of said kettle opposite the endinto which said comestible is introduced.
 7. The apparatus as defined inclaim 6 wherein said third oil distribution means is disposed above thesurface level of the chip-oil slurry and includes a plurality oflongitudinally extending trough plates having orifices therein.
 8. Theapparatus as defined in claim 6 wherein an outlet manifold means isprovided in said kettle intermediate the ends of said kettle and is influid communication with said third oil distribution means.
 9. Theapparatus as defined in claim 8 wherein said outlet manifold means isgenerally disposed beneath said second oil distribution means andincludes a perforated plate means.
 10. The apparatus as defined in claim8 wherein a second outlet manifold means is provided in said kettle inthe end thereof having said third oil distribution means and is in fluidcommunication with a heating means for raising the temperature of saidoil to that necessary to treat said comestible.
 11. The apparatus asdefined in claim 10 wherein said heater means is in fluid communicationwith said first oil distribution means.
 12. The apparatus as defined inclaim 10 wherein said heater means is in fluid communication with saidfirst and second distribution means.